The present invention relates to a method of recording information by using a recording medium which allows information to be rewritten through irradiation with an energy beam such as a light beam, electron beam or the like. More particularly, the invention is concerned with an information recording method which can be effectively applied to a phase change type disc adapted for recording, erasing and rewriting by using a laser beam.
As methods of recording/erasing information on or from the phase change type optical disc recording medium, there is known a method disclosed, for example, in Japanese Patent Application Laid Open No. JP-A-59-71140. According to this known method, erasing through crystallization of information recorded already on a recording film thereof is accomplished by maintaining the recording film for a relatively long period at a temperature at which the recording film can be crystallized through irradiation of a light spot of elliptic shape having a major axis extending trackwise. Subsequent recording of new information is realized by irradiating an adequately focused circular light beam modulated by the information signal to be recorded. Recently, in the course of studies conducted by the inventors of the present application in an effort to improve the material for the recording film, a method was developed which allows the recording film to be crystallized by means of an adequately focused circular light spot moving on the disc. More specifically, information on the disc could be erased with the circular light spot during one rotation of the disc, and subsequently recording could be accomplished during the single succeeding rotation of the disc through irradiation with the laser beam having power modulated correspondingly. Further, by modulating the laser power in accordance with the information signal between the crystallizing power level and the amorphizing power level, rewriting of information could be accomplished in the course of the single revolution of the disc.
However, in the case of the abovementioned technique, rate or speed of the change in atomic arrangement (e.g. crystallization) in the recording film has to be further increased when the rotating speed of the disc is increased with a view to realizing higher information transfer rate. In that case, even when the crystalline material is molten under irradiation by the energy beam (e.g. laser beam), the atomic arrangement resumes the original state (e.g. through recrystallization) during cooling after the irradiation, making it impossible to bring about the change in the atomic arrangement in the reverse direction (e.g. amorphization).